The effect of polishing systems on microleakage of tooth-coloured restoratives. Part 2: composite and polyacid-modified composite resins

Impact of Polishing Systems on the Surface Roughness and Microhardness of Nanocomposites

AIM

The aim of this article is to evaluate the influence of finishing and polishing techniques on the surface roughness and microhardness of two composite resins with two different types of polishing systems.

MATERIALS AND METHODS

A total of 30 disk-shaped specimens of nanocomposite Filtek™ Z350 and Ceram-X® were prepared. They were divided into three groups. The control group (n = 10) received no finishing and polishing. The remaining specimens were divided into two groups, and they received polishing and finishing either with PoGo or Sof-Lex system. After the polishing procedures, average surface roughness (Ra) was assessed with a surface profilometer. The microhardness was determined using a Vickers hardness test. The data were tabulated and analyzed.

RESULTS

The smoothest surfaces were noticed with the control group (Mylar strips) in both composite materials tested. The PoGo one-step polishing system showed significantly better surface roughness compared with the Sof-Lex polishing system. The microhardness did not show any significant variations after finishing and polishing.

CONCLUSION

It can be concluded that the use of PoGo® one-step polishing system resulted in smoother surface with both composite materials studied compared with the Sof-Lex system. The finishing and polishing system had little influence on the surface microhardness.

CLINICAL SIGNIFICANCE

The finishing procedure and polishing system can affect the physical properties and performance of resin composites.

The Influence of One-step Polishing Systems on the Surface Roughness and Microhardness of Nanocomposites

One-step polishing systems exhibited similar or better surface roughness values when compared to multi-step polishing systems. In all groups, mylar-strip created surfaces showed lower microhardness values than polished surfaces. Different polishing procedures did not effect the microhardness of nanocomposites. One-step polishing systems may be a good choice for polishing nanocomposites, resulting in reduced chair time.

Effect of polishing techniques and time on surface roughness, hardness and microleakage of resin composite restorations

This study evaluated the effects of immediate and delayed polishing on the surface roughness, microhardness and microleakage of a microfilled (Filtek A110) and a hybrid (Filtek Z250) resin composite. Standardized preparations were made on the buccal surfaces of 256 bovine teeth; half were restored with each composite (128 teeth per composite). Immediately after curing, gross finishing was carried out with #280 sandpaper. The specimens restored with each composite were divided into two subgroups. The first group (IM) was polished immediately after gross finishing, using three different systems (n=16): Sequence A, Sof-Lex; Sequence B, Flexicups and Sequence C, Flexicups + Jiffy Polishing Brush + Flexibuffs. The specimens were then stored for three weeks in saline 37 degrees C. The second group (DE) was stored for two weeks, then polished with the same systems and stored for one additional week. The controls (n=16) were analyzed without polishing. Five readings per specimen were taken for surface roughness and hardness. After immersion in basic fuchsin, microleakage was evaluated (40x) using standardized scores. The data were analyzed at a significance level of 0.05, with analysis of variance and an SNK test (surface roughness and microhardness) or with Kruskal-Wallis (microleakage). In both composites, only for the sequential technique was there an influence of delay in polishing on roughness (Ra). Flexicups exhibited the highest Ra of the three systems. The IM and Filtek Z-250 groups showed higher hardness than the DE and Filtek A-110 groups, respectively. Dentin margins showed more leakage than enamel margins; the sequential technique produced more leakage than the other techniques in dentin (p<0.05) and delay of polishing was not significant in the majority of situations. In conclusion, several conditions--composite, time and polishing technique--had a significant influence on surface roughness, hardness and microleakage. Generally, immediate polishing produced no detrimental effect compared to delayed polishing.